[Resistance of yeasts to polyene antibiotics].

The strains of Saccharomyces cerevisiae yeast with mutations in two genes NYS3 NYS4 were obtained by tetrad analysis. Sterol fraction of these mutants contains two sterols: ergosta-7-en-3 beta-ol (fungisterol) and ergosta-7,24-dien-3 beta-ol (episterol). The findings allowed to testify the sequence of the ergosterol biosynthesis reactions.

[The level of cytochrome P-450 in Saccharomyces cerevisiae with disruptions of various stages of sterol synthesis].

A spectral analysis of cytochromes P-450 in Saccharomyces cerevisiae cells and in mutant strains accumulating the ergosterol biosynthesis intermediates was carried out. Glucose repression and semianaerobiosis were found to induce cytochrome P-450 synthesis. No differences in the cytochrome P-450 content in mutant nys 3, nys 4 and parent strains were observed.

[The effect of oxygen deficiency on the stability of the yeast Saccharomyces cerevisiae to the polyenic antibiotic nystatin].

Oxygen deficiency was shown to affect the resistance of different Saccharomyces cerevisiae strains to nystatin, a polyenic antibiotic. This resistance decreased upon oxygen deficiency in the wild-type strains alpha'1 and 7A-P192 as well as in the mutant strains NYS 2, NYS 3 and NYS 4, but remained unchanged in the mutants NYS-1 and NYS 5. The qualitative composition of sterols was studied in the strains with a modified ergosterol synthesis, which were grown under the conditions of oxygen deficiency.